Sources of Variation in Mercury Levels in Arctic-breeding Shorebirds A thesis submitted to the College of Graduate and Postdoctoral Studies in partial fulfillment of the requirements for the Degree of Master of Science in the Department of Biology University of Saskatchewan By Katelyn Luff, B.Sc. © Copyright Katelyn Luff, May 2019. All rights reserved. PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a Postgraduate degree from the University of Saskatchewan, I agree that the Libraries of this University may make it freely available for inspection. I further agree that permission for copying of this thesis in any manner, in whole or in part, for scholarly purposes may be granted by the professor or professors who supervised my thesis work or, in their absence, by the Head of the Department or the Dean of the College in which my thesis work was done. It is understood that any copying or publication or use of this thesis or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be made of any material in my thesis. Requests for permission to copy or to make other uses of materials in this thesis in whole or part should be addressed to: Head of the Department of Biology University of Saskatchewan 112 Science Place Saskatoon, Saskatchewan S7N 5E2 Canada Or Dean College of Graduate and Postdoctoral Studies University of Saskatchewan 116 Thorvaldson Building, 110 Science Place Saskatoon Saskatchewan S7N 5C9 Canada Recommended Citation: Luff, K M. 2019. Sources of variation in mercury levels in Arctic-breeding shorebirds. MSc Thesis, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. i ABSTRACT After long-range transport, atmospheric mercury is deposited in Arctic ecosystems via precipitation and can then accumulate in wetlands, where it is subject to methylation at spring thaw. Arctic-nesting shorebirds that forage in wet areas can thus be exposed to significant amounts of methylmercury – the most toxic form of mercury – as it is released from melting snow. Shorebirds that breed during this early period of snow melt and those that forage at higher trophic levels may have increased mercury levels. To my knowledge however, relationships between timing of breeding, trophic status, and mercury levels have not been evaluated in shorebirds. To investigate the extent to which mercury levels change through time and across trophic levels, I analysed blood and egg samples from two northern-breeding shorebird species − Semipalmated Sandpiper (Calidris pusilla; hereafter sandpiper) and Semipalmated Plover (Charadrius semipalmatus; hereafter plover). Both species are locally abundant and have similar arrival times to their breeding grounds, but differ in foraging preference, with plovers generally feeding at higher trophic levels than sandpipers. Blood and egg samples were collected from incubating shorebirds and analyzed for total mercury content (THg). In addition, blood samples were analysed for stable isotopes (δ13C and δ15N). Mean egg THg ranged from 0.07 – 0.52μg/g wet weight and did not reach published thresholds associated with reduced reproduction (0.70 μg/g wet weight). Consistent with an effect of phenology, I observed a decline in mercury with later breeding. For every day that clutch initiation was delayed, THg declined by 0.006 ± 0.003 μg/g wet weight in eggs. Among adult birds, sandpipers had higher THg levels than plovers (p < 0.001), and males had higher THg than females in both species (p < 0.001). Mean blood THg concentrations in male sandpipers approached thresholds associated with adverse effects; 37.5% of initial blood samples (n = 3) exceeded the described 1.0 μg/g wet weight threshold. Sandpipers had higher δ15N values than plovers, suggesting that sandpipers forage at a higher trophic level at Karrak Lake than originally described elsewhere. When species was used as a proxy for trophic status in egg mercury analyses, the same trend was apparent; sandpipers had higher mean egg THg (0.22 ± 0.09 μg/g wet weight) than plovers (0.16 ± 0.05 μg/g wet weight). Taken together, these results suggest that contrasting avian life history strategies, such as timing of breeding and foraging habits, can have relevance to THg exposure that warrant further consideration. Future research ii should focus on adjusting methodology to reduce variation among samples (i.e. collecting first- laid eggs only) and determining whether observed mercury concentrations are impacting the survival of breeding Arctic shorebirds. iii ACKNOWLEDGEMENTS First and most of all, I’d like to thank my graduate supervisor Dr. Kirsty Gurney, for her constant support and guidance throughout this endeavor, I’m very grateful for all of it and in more ways than I could ever possibly put into words. Thank you to my committee members: Dr. Ray Alisauskas, Dr. Christy Morrissey, and Dr. Paul Smith, who always provided thoughtful advice and posed challenging questions. As well, they provided support for banding opportunities, fieldwork accommodation, and sample collection. Thank you to Scott Freeman, who mentored me throughout the data collection stage, and taught me much of what I know about trapping and handling shorebirds, as well as Ella Lunny who was a fantastic person to have out in the field. Thank you to the field crews at the Karrak Lake research camp in 2016 and 2017, who helped to make the place feel like a home away from home: Dana Kellett, Anne Blondin, Kelly Likos, Elaine Kennedy, Sasha Ross, Deborah Hawkshaw, Toren Johnson, Brain Malloure, Gustaf Samelius, Doug Stern , Greg and Rory Fenech, Stephane Ménu, Melanie Rose, Maliya Cassels, Keaton Schmidt, and Audrey Trembly. I’d like to thank my parents, Dan and Grace Luff for their constant support all while being several provinces away. As well as for their patience while I was in the field, as they often had to put up with very short, sporadic satellite phone calls. I’d also like to thank my sister, Alison Luff who is always willing to lend an ear and a laugh. Thank you to my partner, Nate Troesch who has provided moral support and constant encouragement throughout this endeavor, and who never doubted me, even when I would doubt myself. Thank you for all the support, as well as your patience while I was in the field, as those sporadic, satellite phone calls were commonplace throughout the summer. Finally, I’d like to thank everyone in Saskatoon and beyond who I’ve had the pleasure of meeting and forming friendships with while on this journey, I am extremely thankful to be able to know all of you. iv TABLE OF CONTENTS PERMISSION TO USE ................................................................................................................... i ABSTRACT .................................................................................................................................... ii ACKNOWLEDGEMENTS ........................................................................................................... iv TABLE OF CONTENTS ................................................................................................................ v LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ........................................................................................................................ x LIST OF ABBRIVIATIONS ........................................................................................................ xii INTRODUCTION .......................................................................................................................... 1 1. 1. THESIS OBJECTIVES, HYPOTHESES AND PREDICTIONS ...................................... 3 1. 1. 1. Nesting Phenology ................................................................................................ 3 1. 1. 2. Trophic Status ....................................................................................................... 3 1. 1. 3. Sex Differences ..................................................................................................... 4 METHODS ..................................................................................................................................... 7 2. 1. STUDY SITES.................................................................................................................... 7 2.1.1 Ahiak-Queen Maud Migratory Bird Sanctuary, Nunavut .............................................. 7 2.1.2 Coats Island, Nunavut .................................................................................................... 7 2.1.3 East Bay (Qaqsauqtuuq) Migratory Bird Sanctuary, Nunavut ...................................... 7 2. 2. FIELD METHODS ............................................................................................................. 8 2.2.1 Egg Collections .............................................................................................................. 8 2.2.2 Trapping of Adult Birds ................................................................................................. 9 2.2.3 Blood Collections......................................................................................................... 10 2.2.4 Environmental Data ....................................................................................................